<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>小算法</title>
		<style type="text/css">
			.w {
				width: 800px;
				height: 1400px;
				background-color: pink;
				margin: 0 auto;
			}
			.fixed {
				position: fixed;
				left: 50%;
				margin-left: 400px;
				margin-top: 100px;
				width: 50px;
				height: 150px;
				background-color: #00ffff;
			}
		</style>
	</head>
	<body>
		<div class="fixed">固定</div>
		<div class="w">版心盒子 宽800px</div>
	</body>
</html>
